The Sand Hills of Nebraska are a unique Great Plains prairie ecosystem. The rolling dunes, rising to 300 feet, cover about a quarter of the state, and because the grasses and wildflowers there are adapted to wet, sandy soil, many grow nowhere else. Thousands of ponds and lakes dot the Sand Hills, nourishing the Ogallala Aquifer.

This region is an unlikely ground zero for a growing rebellion against a different kind of sand — the Athabascan oil sands of Alberta, 1,400 miles to the north. But that is precisely what is happening as energy companies seek to construct a pipeline from Alberta’s tar sands — the second-largest petroleum deposit in the world, after Saudi Arabia — across the length of the U.S. to refineries in Texas, passing through the Sand Hills on its way.

And the so-called Keystone XL pipeline is not the only tentacle of the tar sands poised to spread across North America: Energy companies are seeking to build a second pipeline to carry tar sands oil across the wild heart of British Columbia, while other firms are proposing to truck gargantuan equipment for the tar sands project along narrow roads in one of most remote parts of the northern Rocky Mountains.

Environmentalists, farmers, ranchers, elected officials, native people, and a host of others have risen up in opposition to the potential environmental threats posed by the expanding reach of Alberta’s tar sands. Some opponents are concerned that pipelines or oversized equipment running through their communities pose an unacceptable environmental risk. But for others, the battle is about something far larger. They believe that wreaking so much environmental destruction to continue expanding supplies of planet-warming fossil fuels is fundamentally wrong, noting that the tar sands project has razed hundreds of square miles of boreal forest, led to the creation of dozens of toxic tailings ponds, and released vast quantities of CO2. And they are convinced that choking off the tar sands pipelines is a way of stopping, or at least hampering, the development of the Alberta tar sands themselves.

Indeed, the fight over the tar sands pipelines has become a proxy battle between two diametrically opposed worldviews: Those who see the planet as heading toward irreversible environmental harm, driven largely by human CO2 emission from fossil fuels, and those who say that the U.S. needs oil at almost any environmental cost to keep its economy growing.

“The pipeline has become a symbol of where America is going,” says Jane Kleeb, director of BOLD Nebraska, a group working to protect the unique ecology of the Sand Hills. “We’re concerned about climate change, absolutely. America is smart enough to figure out how to do clean energy.”

Among the growing protests over Alberta’s tar sands and the proposed pipelines are a series of acts of civil disobedience planned in Washington, D.C., for the last two weeks of August. The campaign, Tar Sands Action, will feature protests at the White House and will include author and environmental activist Bill McKibben, NASA climate scientist James Hansen, and Canadian scientist and broadcaster, David Suzuki.

Roughly 173 billion barrels of Alberta tar sands reserves, worth more than $15 trillion, underlay an area the size of Florida, making it by far the largest petroleum deposit in North America. The strange solid or semi-solid oil, called bitumen, is essentially mined, and doing so means digging up large tracts of boreal forest and releasing a lot of CO2, which is why critics call the product of the tar sands “dirty oil.”

But supporters of the tar sands and the pipelines say that the “dirty oil” rap is unfair. Canada’s environment minister, Peter Kent, says tar sands crude creates just 1 percent of the greenhouse gas emissions generated annually by U.S. coal-fired power plants. It’s really “ethical oil,” he says, because the profits won’t go to corrupt dictators or civil wars.

Oil companies have limited refining capacity for the dense crude in Alberta, and that’s where the biggest pipeline project, Keystone XL, figures in. Each day the proposed Keystone XL pipeline — to be built by Calgary-based TransCanada Corporation — would move 910,000 barrels of a slurry of bitumen, natural gas, and undisclosed chemicals through a 36-inch-diameter, high-pressure pipe, buried four feet underground. The nearly 1,700-mile route would run from Hardisty, Alberta, through Saskatchewan, Montana, South Dakota, Nebraska (including 92 miles of the Sand Hills), and Oklahoma. After connecting with an existing pipeline in Nebraska, the new Keystone XL would begin again in Cushing, Oklahoma and continue on to Houston and Port Arthur, Texas. There, company officials say, they would have the special refining capacity they need.

The $7 billion pipeline, which must be approved by the U.S. State Department and the Environmental Protection Agency (EPA), has drawn both opposition and support across its route. But it has run into the fiercest resistance in the conservative farming state of Nebraska, largely because the pipeline would cross the Sand Hills. Should the toxic brew leak, it could pollute not only the water there, but could seep into portions of the Ogallala Aquifer, the 174,000-square-mile underground reservoir, fed in part by water from the Sand Hills.

Spills are not a far-fetched scenario. In a year of operation, a similar pipeline in the U.S. — the existing Keystone, also owned by TransCanada Corporation — had 11 spills. Most of them were tiny, but the largest, in southeastern North Dakota, was 21,000 gallons, and federal officials temporarily suspended the company’s operating permit. And last year a 30-inch oil pipeline owned by Enbridge, another Canadian pipeline company, suffered a 4-foot-long rupture and spilled nearly 20,000 barrels — 840,000 gallons — of oil into the Kalamazoo River in Michigan, killing much of the aquatic life for miles. It was the worst spill ever in the Midwest.